The default language for this game and the clone is English but strangely it switch to Japanese.
In the DIP Switches settings English language is selected by default.

UPDATE:
I've found a fix for this problem:
By default, in the "Dip Switches" settings, the the first "Unknown" option is set to "Off" and the "Language" is set to "English".
You have to set the "Unknown" option to "On" then exit the emulator.
Open the emulator again then start the game.
From this moment the game will display English language.
This fix will always work.